I have used east coast auto electric alternators with real good luck.

As far as 12 vs 16, there are advantages and disadvantages. On my last build when I saw I had to reduce a bunch of things, and just would really be using the extra voltage for cranking I decided against it.

Sometimes i think people have problems starting, so just default to 16V when in fact the issues are elsewhere in the electrical system. Running proper size cables for alternator, starter etc. are important. I don't use chassis grounds, my whole system grounds back to battery, I firmly believe that helps a lot.

i like deka batteries.